材料手册 5 陶瓷、耐火材料、玻璃、聚合物、弹性体 英文版 19.docx

602 Ceramics. Refractories, and Glasses
Table 10 J. Digestion conditions for various bauxitic ore
Bauxitic
ore
Digestion reaction Conditions
Gibbsitic 2A1O(OH).H,O + 2NaOH —> ZNaAlO, +
4H
2
O
Atmospheric pressure
135°C<T<150°C
Boehmitic 2A1O(OH) + 2NaOH —> 2NaA10, + 2H,0 Atmospheric pressure
205°C< T<245°C)
Diasporic 2A10(0H) + 2NaOH —> ZNaAlO, + 2H,0 High pressure (3.5-4 MPa)
T>250°C
Comminution. First, bauxite run-of-mine ore is crushed using a jaw crusher to produce coarse
particles below 30 mm in diameter. It is then washed with water in order to remove clay minerals
and silica in an operation called desliming. The washed and crushed ore is then mixed with the
recycled caustic liquor downstream from the Bayer process, then ground more finely providing a
suspension or slurry of bauxite with 90% of particles with a size less than 300 pm (48 mesh Tyler).
This grinding step is required to increase the specific surface area of the bauxite in order to
improve the digestion efficiency. The recycled liquor comes from the filtration stage of the hydrate